U.S. patent application number 11/654251 was filed with the patent office on 2008-07-17 for computed tomography cargo inspection system and method.
This patent application is currently assigned to GE Homeland Protection, Inc.. Invention is credited to Joseph Bendahan.
Application Number | 20080170655 11/654251 |
Document ID | / |
Family ID | 39617773 |
Filed Date | 2008-07-17 |
United States Patent
Application |
20080170655 |
Kind Code |
A1 |
Bendahan; Joseph |
July 17, 2008 |
Computed tomography cargo inspection system and method
Abstract
An X-ray computed tomography scanning system for inspecting an
object includes a platform configured to support the object. The
platform is rotatable about an axis and movable in a direction
parallel to the axis. At least one X-ray source is fixedly
positioned with respect to the platform and configured to transmit
radiation through the object. At least one X-ray detector is
fixedly positioned with respect to the platform. The at least one
X-ray detector is configured to detect the radiation transmitted
through the object and generate a signal representative of the
detected radiation.
Inventors: |
Bendahan; Joseph; (San Jose,
CA) |
Correspondence
Address: |
PATRICK W. RASCHE;ARMSTRONG TEASDALE LLP
ONE METROPOLITAN SQUARE, SUITE 2600
ST. LOUIS
MO
63102-2740
US
|
Assignee: |
GE Homeland Protection,
Inc.
|
Family ID: |
39617773 |
Appl. No.: |
11/654251 |
Filed: |
January 17, 2007 |
Current U.S.
Class: |
378/9 |
Current CPC
Class: |
G01V 5/005 20130101;
G01V 5/0041 20130101; G01V 5/0091 20130101; G01V 5/0069
20161101 |
Class at
Publication: |
378/9 |
International
Class: |
A61B 6/00 20060101
A61B006/00 |
Claims
1. An X-ray computed tomography scanning system configured for
inspecting an object for contraband, said X-ray computed tomography
scanning system comprising: a base defining an axis; a frame
movably coupled to said base, said frame movable with respect to
said base in a direction parallel to the axis; a platform
configured to support the object, said platform rotatably coupled
to said frame, said platform movable with said frame and rotatable
with respect to said frame about the axis; at least one X-ray
source fixedly positioned with respect to said platform, said at
least one X-ray source configured to transmit radiation through the
object; and at least one X-ray detector fixedly positioned with
respect to said platform, said at least one X-ray detector
configured to detect the radiation transmitted through the object
and generate a signal representative of the detected radiation.
2. (canceled)
3. An X-ray computed tomography scanning system in accordance with
claim 2 wherein said at least one X-ray source is mounted to a
first tower positioned with respect to said base.
4. An X-ray computed tomography scanning system in accordance with
claim 3 wherein said at least one X-ray detector is mounted to a
second tower positioned with respect to said base.
5. An X-ray computed tomography scanning system in accordance with
claim 1 wherein said at least one X-ray source comprises a megavolt
X-ray generator.
6. An X-ray computed tomography scanning system in accordance with
claim 1 wherein said at least one X-ray source comprises an X-ray
source configured to selectively emit radiation at at least one
energy distribution.
7. An X-ray computed tomography scanning system in accordance with
claim 1 wherein said at least one X-ray source comprises a first
X-ray source configured to emit radiation at a first energy
distribution and a second X-ray source configured to emit radiation
at a second energy distribution different from the first energy
distribution.
8. An X-ray computed tomography scanning system in accordance with
claim 1 wherein said at least one X-ray detector comprises a
plurality of X-ray detectors.
9. An X-ray computed tomography scanning system in accordance with
claim 1 further comprising: a data collection system in signal
communication with said at least one X-ray detector, said data
collection system configured to receive the generated signals and
produce an image of the object; and a processor operatively coupled
to said data collection system, said processor configured to
process the produced image for facilitating determining the
material content of the object.
10. An X-ray computed tomography scanning system in accordance with
claim 9 wherein said processor is configured to produce a map of at
least one of a CT number, density and atomic number of the scanned
object.
11. An X-ray computed tomography scanning system in accordance with
claim 1 further comprising: at least one neutron and gamma-ray
detector positioned with respect to said platform, said at least
one neutron and gamma-ray detector configured to detect radiation
produced by fission of a fissile material within the object and
generate a signal representative of detected radiation; a data
collection system operatively coupled to said at least one neutron
and gamma-ray detector, said data collection system configured to
receive the generated signal; and a processor operatively coupled
to said data collection system, said processor comprising an
algorithm for facilitating detecting a presence of fissile
material.
12. An X-ray computed tomography scanning system in accordance with
claim 11 wherein said at least one neutron and gamma-ray detector
is configured to perform a passive scan of the object for
facilitating detecting radioactive materials.
13. A method for inspecting a container for contraband, said method
comprising: positioning the container on a platform configured to
support the container, the platform rotatably coupled to a frame
that is movably coupled to a base defining an axis, the frame
movable with respect to the base in a direction parallel to the
axis, and the platform movable with the frame and rotatable with
respect to the frame about the axis; producing X-ray beams having
at least one energy distribution and transmitting the X-ray beams
through the container as the container rotates about the axis and
moves in a direction parallel to the axis; detecting the X-ray
beams transmitted through the container with an array of detectors
to generate signals representative of the detected radiation; and
processing the signals to produce images of the container and
contents of the container to generate a map for the container
including at least one of a CT number, a density and an atomic
number corresponding to the contents within the container.
14. A method in accordance with claim 13 wherein producing X-ray
beams further comprises fixedly positioning at least one X-ray
source with respect to the platform, the at least one X-ray source
configured to transmit radiation through the container.
15. A method in accordance with claim 13 further comprising
selectively emitting radiation from the at least one X-ray source
at at least one energy distribution.
16. A method in accordance with claim 13 further comprising
emitting radiation from a first X-ray source of the at least one
X-ray source at a first energy distribution and emitting radiation
from a second X-ray source of the at least one X-ray source at a
second energy distribution different from the first energy
distribution.
17. A method in accordance with claim 13 wherein detecting the
X-ray beams further comprises fixedly positioning at least one
X-ray detector with respect to the platform, the at least one X-ray
detector configured to detect the radiation transmitted through the
container and generate a signal representative of the detected
radiation.
18. A method in accordance with claim 13 further comprising
analyzing the images to determine a type of material contained
within the container, wherein the images are analyzed by at least
one of an automatic process and a person.
19. A method for X-ray computed tomography scanning of a container
supported on a platform for inspecting contents of the container,
said method comprising: providing a base defining a first axis and
a frame movably coupled to the base; moving the frame with respect
to the base in a direction parallel to the first axis; rotating the
platform coupled to the frame, the platform rotatable with respect
to the frame about the first axis; emitting an X-ray beam from at
least one X-ray source fixedly positioned with respect to the
platform and transmitting the X-ray beam through the container; and
detecting the transmitted X-ray beam by at least one X-ray detector
fixedly positioned with respect to the platform.
20. A method in accordance with claim 19 further comprising:
generating signals representative of the detected X-ray beam;
transmitting the generated signals from the at least one X-ray
detector to a data collection system in signal communication with
the at least one X-ray detector, the data collection system
configured to receive the generated signals; processing the signals
to reconstruct at least one image of a CT number, a density and an
atomic number of contents; and inferring from the at least one
reconstructed image the contents.
21. A method in accordance with claim 19 further comprising:
inducing fission of a fissile material contained within the
container; detecting radiation produced by the fission with at
least one neutron and gamma-ray detector positioned with respect to
the platform, the at least one neutron and gamma-ray detector
configured to generate a signal representative of detected
radiation; and processing the detected radiation to facilitate
detecting a presence of fissile material.
22. A method in accordance with claim 21 further comprising
confirming a presence of fissile material using an algorithm for
detecting fissile material.
23. A method in accordance with claim 21 further comprising
passively scanning the container to facilitate detecting
radioactive materials.
24. A method in accordance with claim 19 further comprising
collecting data in one of a step-and-shoot mode and a helical
mode.
25. An X-ray computed tomography scanning system comprising: a base
defining an axis; a frame movably coupled to said base, said frame
movable with respect to said base in a direction parallel to the
axis; a platform configured to support the object, said platform
rotatably coupled to said frame, said platform movable with said
frame and rotatable with respect to said frame about the axis; at
least one X-ray source positioned with respect to said platform,
said at least one X-ray source configured to transmit radiation
through the object and induce fission of a fissile material within
the object; at least one neutron and gamma-ray detector positioned
with respect to said platform, said at least one neutron and
gamma-ray detector configured to detect radiation produced as a
result of fission, said at least one neutron and gamma-ray detector
configured to generate a signal representative of detected
radiation; and a data collection system operatively coupled to said
at least one neutron and gamma-ray detector, said data collection
system configured to detect a presence of fissile material based at
least partially on the generated signal.
26. An X-ray computed tomography scanning system comprising: a base
defining an axis; a frame movably coupled to said base, said frame
movable with respect to said base in a direction parallel to the
axis; a platform configured to support the object, said platform
rotatably coupled to said frame, said platform movable with said
frame and rotatable with respect to said frame about the axis; at
least one neutron and gamma-ray detector positioned with respect to
said platform, said at least one neutron and gamma-ray detector
configured to passively detect a presence of radioactive material,
said at least one neutron and gamma-ray detector configured to
generate a signal representative of detected radiation; and a data
collection system operatively coupled to said at least one neutron
and gamma-ray detector, said data collection system configured to
detect a presence of radioactive material based at least partially
on the generated signal.
27. An X-ray computed tomography scanning system in accordance with
claim 26 wherein said platform is rotatable to facilitate data
collection.
28. A high-energy, high throughput computed tomography (CT)
scanning system configured for inspecting an object for contraband,
said high-energy, high throughput CT scanning system comprising: a
platform configured to support the object, said platform at least
one of rotatable about an axis and movable in a direction parallel
to the axis, said platform positionable in a plurality of step over
positions to facilitate scanning at least a portion of the object;
a high-energy radiation source fixedly positioned with respect to
said platform, said high-energy radiation source configured to
produce radiation that is transmitted through the object as the
object rotates with said platform; an array of detectors fixedly
positioned with respect to said platform, said array of detectors
configured to measure radiation transmitted through the object and
generate at least one signal representative of the detected
radiation; and a processor configured to reconstruct a plurality of
images in real time based at least partially on the at least one
signal received from said array of detectors.
29. A high-energy, high throughput CT scanning system in accordance
with claim 28 further comprising a conveyor operatively coupled to
said platform to facilitate moving a plurality of objects through
said high-energy CT scanning system.
30. A high-energy, high throughput CT scanning system in accordance
with claim 28 further comprising localized shielding positioned
about at least a portion of said high-energy CT scanning
system.
31. A high-energy, high throughput CT scanning system in accordance
with claim 28 wherein said high-energy radiation source produces
X-ray radiation.
32. A high-energy, high throughput CT scanning system in accordance
with claim 28 wherein said high-energy radiation source generates
radiation having an energy distribution of at least about 1 MV.
33. A high-energy, high throughput CT scanning system in accordance
with claim 28 wherein said high-energy radiation source comprises a
multiple energy system.
34. A high-energy, high throughput CT scanning system in accordance
with claim 28 wherein said high-energy CT scanning system is
configured to at least one of automatically and by user inspection
detect contraband within the object.
35. A high-energy, high throughput CT scanning system in accordance
with claim 34 wherein, during detection by user inspection, said
high-energy CT scanning system further configured to provide images
for visually inspection of the object to facilitate on-screen
resolution of detected contraband.
36. A high-energy, high throughput CT scanning system in accordance
with claim 28 further comprising a subsystem comprising at least
one of an array of neutron detectors and an array of gamma
detectors, said subsystem configured to at least one of passively
detect at least one of neutron radiation and gamma radiation
emitted from the object and detect a result of an active
interrogation of the object to confirm a presence of nuclear
material within the object.
37. A high-energy, high throughput CT scanning system in accordance
with claim 28 wherein said high-energy radiation source is
configured to generate low energy X-rays and high energy X-rays in
a high speed switching mode such that the object is scanned only
one time to facilitate high throughput.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to cargo inspection systems
and, more particularly, to cargo inspection systems incorporating
computed tomography (CT) to inspect cargo for contraband and
methods for operating the same.
[0002] Since the events of Sep. 11, 2001, the Department of
Homeland Security has increased security dramatically in U.S.
airports. Such security efforts include screening passengers and
carry-on bags and luggage for contraband including explosive
materials.
[0003] Many of these systems employ single or few multi-view x-ray
transmission technology. Although, these systems enable the
detection of weapons and blades, for example, they lack the
capability of detecting explosives with a low false alarm rate.
[0004] CT provides a quantitative measure of material
characteristics, regardless of location or the superposition of
objects; a substantial advantage over conventional and multi-view
x-ray transmission and radioisotope-based imaging systems. In a CT
scanner, a large number of precise x-ray "views" are obtained at
multiple angles. These views are then used to reconstruct planar or
volumetric images. The image is a mapping of the x-ray mass
attenuation value for each volume element (or voxel) within the
imaged volume.
[0005] Systems employing CT are widely employed in airports around
the world in checked luggage to detect explosives that pose a
threat to aviation safety. These systems employ an x-ray source and
opposing detectors that rotate around a horizontal axis while the
suitcase is translated along the same horizontal axis.
[0006] While such screening processes are also reliable and
suitable for break-bulk cargo, there is a need for inspecting large
crates, pallets and containers too large to inspect with
conventional checked-luggage scanning systems. Further, it is too
time consuming to remove and inspect the contents of each cargo
container before loading the container for delivery to the
destination. Only a portion of air cargo containers are inspected
using currently available technologies including manual inspection,
canine inspection and/or trace detection. It is recognized that
these inspection methods must be improved for automation and/or to
obtain greater detection.
[0007] Computed Tomography for objects larger than checked luggage
requires a high-energy x-ray generator to penetrate the more
attenuating objects and a large array of high-energy detectors to
cover the large objects and detect the higher energy of the
radiation.
[0008] Systems employing these principles are in use for
Non-Destructive Testing (NDT) of machine parts, jet engines and
rockets, for example. These systems are tailored for NDT
applications with characteristics not suitable for contraband
inspections. In addition, the scanning and image reconstruction
processes are very slow.
[0009] A CT scanning system has been described that includes a
rotatable table that supports a container and an x-ray source and
an opposing x-ray detector that are movable parallel to the
rotational axis of the table to scan cargo containers for the
detection of explosives and other contraband.
BRIEF DESCRIPTION OF THE INVENTION
[0010] In one aspect, an X-ray computed tomography scanning system
is provided for inspecting an object. The X-ray computed tomography
scanning system includes a platform configured to support the
object. The platform is rotatable about an axis and movable in a
direction parallel to the axis. At least one X-ray source is
fixedly positioned with respect to the platform and configured to
transmit radiation through the object. At least one X-ray detector
is fixedly positioned with respect to the platform. The at least
one X-ray detector is configured to detect the radiation
transmitted through the object and generate a signal representative
of the detected radiation.
[0011] In another aspect, a method is provided for inspecting a
container for contraband. The method includes positioning the
container on a platform configured to support the container. The
platform is rotatable about an axis and movable in a direction
parallel to the axis. X-ray beams are produced having at least one
energy distribution and transmitted through the container as the
container rotates about the axis and moves in a direction parallel
to the axis. The X-rays transmitted through the container are
detected with an array of detectors that generate signals
representative of the detected radiation. The signals are processed
to produce images of the container and its contents to generate a
map for the container including at least one of a CT number, a
density and an atomic number corresponding to the contents within
the container.
[0012] In another aspect, a method is provided for X-ray computed
tomography scanning a container supported on a platform for
inspecting contents of the container. The method includes providing
a base defining a first axis and a frame movably coupled to the
base. The frame moves with respect to the base in a direction
parallel to the first axis. The platform coupled to the frame
rotates with respect to the frame about the first axis. An X-ray
beam is emitted from at least one X-ray source fixedly positioned
with respect to the platform and transmitted through the container.
The transmitted X-ray beam is detected by at least one X-ray
detector fixedly positioned with respect to the platform.
[0013] In another aspect, an X-ray computed tomography scanning
system is provided. The X-ray computed tomography scanning system
includes a platform configured to support an object. At least one
X-ray source is positioned with respect to the platform and is
configured to transmit radiation through the object and induce
fission of a fissile material within the object. At least one
neutron and gamma-ray detector positioned with respect to the
platform is configured to detect radiation produced as a result of
fission. The at least one neutron and gamma-ray detector is further
configured to generate a signal representative of detected
radiation. A data collection system is operatively coupled to the
at least one neutron and gamma-ray detector. The data collection
system is configured to detect a presence of fissile material based
at least partially on the generated signal.
[0014] In another aspect, an X-ray computed tomography scanning
system is provided. The X-ray computed tomography scanning system
includes a platform configured to support an object. At least one
neutron and gamma-ray detector is positioned with respect to the
platform. The at least one neutron and gamma-ray detector is
configured to passively detect a presence of radioactive material
and to generate a signal representative of detected radiation. A
data collection system is operatively coupled to the at least one
neutron and gamma-ray detector. The data collection system is
configured to detect a presence of radioactive material based at
least partially on the generated signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of an exemplary X-ray computed
tomography (CT) scanning system.
[0016] FIG. 2 is a perspective view of a portion of the X-ray
computed tomography (CT) scanning system shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention provides a system and method for
effectively inspecting cargo for the presence of contraband
including, without limitation, explosive material, nuclear material
and/or shielding material. In one embodiment, an X-ray computed
tomography (CT) scanning system is utilized for facilitating
inspecting cargo for contraband. The present invention employs an
X-ray CT scanning system having system characteristics, such as
spatial resolution, penetration, scanning and/or reconstruction
speeds that can be tailored for the detection of explosives,
nuclear material and/or other contraband. In a particular
embodiment, the scanning system may include localized shielding to
minimize facility requirements and/or a conveyor or other suitable
transport mechanism operatively coupled to the scanning system to
facilitate moving the cargo through the scanning system.
[0018] The system and method provide a three dimensional image of
the object to map a density and/or an atomic number of the object
being inspected. This information is employed to infer
automatically (without user intervention) the presence of explosive
material, nuclear material and/or shielding material. Further, such
information can also be used for visual inspection and/or
determination of a type of contraband within the object.
Alternatively or in addition, user inspection/on-screen resolution
can also be incorporated to detect or confirm a presence of
explosive material, nuclear material and/or other contraband and
for cargo manifest verification. The system's spatial resolution
facilitates detecting small explosives that pose a threat to
aviation security while also detecting nuclear material and/or
shielding material. The system is also capable of detecting fissile
material and detecting unshielded or partially shielded radioactive
material.
[0019] The present invention is described below in reference to its
application in connection with and operation of a system for
inspecting cargo crates, pallets and/or containers. However, it
will be apparent to those skilled in the art and guided by the
teachings herein provided that the invention is likewise applicable
to any suitable system for scanning containers including, without
limitation, boxes, drums and luggage, transported by water, land
and/or air, as well as other containers and/or objects. Further,
although the present invention is described below in reference to
its application in connection with and operation of a system
incorporating an X-ray computed tomography scanning system for
inspecting cargo crates, pallets and/or containers, it is apparent
to those skilled in the art and guided by the teachings herein
provided that any suitable radiation source including, without
limitation, neutrons or a gamma rays may be used in alternative
embodiments.
[0020] FIG. 1 is a perspective view of an X-ray computed tomography
(CT) scanning system 10 for scanning an object, such as a cargo
container 12, box or drum, to identify the contents and/or
determine the type of material contained within container 12. FIG.
2 is a perspective view of a portion of system 10 shown in FIG. 1.
The term "contents" as used herein refers to any object and/or
material contained within container 12 and may include contraband.
System 10 includes a base 14 defining a first axis 16. As shown in
FIGS. 1 and 2, first axis 16 defines a vertical axis. Base 14 is
fabricated of a suitable material that provides sufficient support
for the system components and the objects positioned on system 10.
A frame 18 is movably coupled to base 14. Frame 18 is movable with
respect to base 14 in at least one direction. In one embodiment,
frame 18 is movable with respect to base 14 in a direction parallel
to first axis 16, e.g., in an upward direction and a downward
direction.
[0021] System 10 further includes a platform 20 that is rotatably
coupled to frame 18. Platform 20 is movable with frame 18 and
rotatable with respect to frame 18. In one embodiment, platform 20
is rotatable with respect to frame 18 about first axis 16 in a
clockwise or counterclockwise rotational direction and movable with
frame 18 with respect to base 14 in an upward direction and a
downward direction parallel to first axis 16. As shown in FIGS. 1
and 2, platform 20 forms a surface 22 for supporting container
12.
[0022] System 10 includes at least one X-ray source 30, such as a
megavolt X-ray generator, fixedly positioned with respect to frame
18 and/or platform 20. In a particular embodiment, X-ray source 30
is fixedly positioned with respect to a first side of frame 18
and/or platform 20. As shown in FIG. 1, X-ray source 30 is mounted
to a first tower 32 positioned with respect to base 14. Each X-ray
source 30 is configured to transmit at least one beam of radiation,
such as a cone beam, through container 12, as described in greater
detail below. In one embodiment, a plurality of X-ray sources 30
are fixedly positioned with respect to platform 20 and configured
to emit radiation of different energy distributions. Alternatively,
each X-ray source 30 is configured to emit radiation of selective
energy distributions, which can be emitted at different times. In a
particular embodiment, system 10 utilizes multiple energy
inspection to obtain an attenuation map for container 12. In a
multiple energy system, such as a dual energy system, a first or
low energy source generates radiation having an energy distribution
of about 2 MV to about 6 MV and a second or high energy source
generates radiation having an energy distribution of about 6 MV to
about 20 MV. It is apparent to those skilled in the art and guided
by the teachings herein provided that the first energy source may
generate radiation having an energy distribution less than about 2
MV and/or greater than about 6 MV and/or the second energy source
may generate radiation having an energy distribution less than
about 6 MV and/or greater than about 20 MV.
[0023] In addition to the production of CT images, multiple-energy
scanning enables the production of density maps and atomic number
of the object contents. This information allows for an improved
identification of the materials contained in container 12. For
example, it allows for accurately distinguishing high-density
tungsten from uranium. In one embodiment, the dual energy scanning
of container 12 includes inspecting container 12 by scanning
container 12 at the low energy and then scanning container 12 at
the high-energy. The data is collected for the low-energy scan and
the high-energy scan to reconstruct the CT, density and/or atomic
number images of container 12 for facilitating identifying the type
of material or contraband within container 12 based on the material
content of container 12, as described in greater detail below.
[0024] In an alternative embodiment, X-ray source 30 includes a
linear accelerator 34 for producing a pulsed X-ray source. In this
embodiment, linear accelerator 34 generates the low energy x-rays
and the high energy x-rays in a high speed switching mode or
interlaced mode such that container 12 is scanned only one time.
This approach allows for higher throughput. In further alternative
embodiments, X-ray source 30 includes a suitable electrostatic
accelerator, a microtron or a betatron or any other type of X-ray
source.
[0025] In one embodiment, container 12 is scanned with at least one
energy distribution. Following analysis of the images, suspicious
areas are selected for a more detailed scan. Improved details are
obtained with longer scanning times and/or improved spatial
resolution.
[0026] At least one X-ray detector 40 is fixedly positioned with
respect to frame 18 and/or platform 20. In one embodiment, X-ray
detector 40 is fixedly positioned with respect to a second side of
frame 18 and/or platform 20 opposing the platform first side. In a
particular embodiment, X-ray detector 40 is mounted to a second
tower 42 positioned with respect to base 14, as shown in FIG. 1.
X-ray detector 40 is configured to detect radiation emitted from
X-ray source 30 and transmitted through container 12. X-ray
detector 40 is configured to cover an entire field of view or only
a portion of the filed of view. Upon detection of the transmitted
radiation, X-ray detector 40 generates a signal representative of
the detected transmitted radiation. The signal is transmitted to a
data collection system and/or processor as described below. In one
embodiment, X-ray detector 40 includes a high-energy detector
configured to cover container 12 partially or completely and detect
radiation energy in an allotted time. In a particular embodiment,
X-ray detector 40 includes an array or plurality of two dimensional
detector elements to detect X-ray transmission through container
12. Upon detection of the transmitted radiation, each X-ray
detector element generates a signal representative of the detected
transmitted radiation. The signal is transmitted to a data
collection system and/or processor as described below.
[0027] System 10 is utilized to reconstruct a CT image of container
12 positioned on surface 22 of platform 20 in real time or non-real
or delayed time. In one embodiment, frame 18 is actuated to move
with respect to base 14 in a direction parallel to first axis 16,
e.g., in an upward direction or a downward direction along first
axis 16. Any suitable drive assembly known to those skilled in the
art and guided by the teachings herein provided may be operatively
coupled to frame 18 to provide such actuation and movement with
respect to base 14. As frame 18 moves with respect to base 14,
platform 20 rotates with respect to frame 18 about first axis 16.
In one embodiment, platform 20 rotates 360.degree. in a first
rotational direction with respect to frame 18. Alternatively,
platform 20 only partially rotates with respect to frame 18. For
example, in a particular alternative embodiment, platform 20
rotates in the first rotational direction about 270.degree. and
then reverses direction to rotate in an opposing second rotational
direction about 270.degree.. It should be apparent to those skilled
in the art and guided by the teachings herein provided that
platform 20 may rotate in either rotational direction and/or for
any suitable degree of rotation to facilitate scanning container
12, as described in greater detail below. In a further alternative
embodiment, container 12 is stationary as system 10 rotates about
first axis 16 and/or moves with respect to container 12 parallel to
first axis 16.
[0028] System 10 is configured to operate in a step-and-shoot mode
and a helical mode. In the step-and-shoot mode, system 10 is
positioned with respect to container 12 to be scanned, with or
without the container rotating and without collecting data. With
system 10 in proper position, the data is collected as container 12
is rotated. In one embodiment, container 12 is continuously rotated
during the step-and-shot mode. Alternatively, in the helical mode,
platform 20 is continuously rotated as frame 18 is translated to
collect data.
[0029] One or more X-ray sources 30, mounted to first tower 32 and
stationary with respect to platform 20, generate X-ray beams having
one or more energy distributions. In one embodiment, X-ray source
30 includes a pulsed X-ray source including linear accelerator 34,
which generates a low energy source and a high energy source in a
high speed switching mode or interlaced mode such that container 12
is scanned only one time. In one embodiment, one or more
collimators (not shown) are positioned between X-ray source 30 and
container 12 to collimate the X-ray beam emitted from each X-ray
source 30 into a suitable beam, such as a cone beam, to reduce
excessive radiation that is not used in imaging container 12 and/or
to minimize scattered radiation.
[0030] X-ray detector 40 detects radiation emitted from X-ray
source 30 and transmitted through container 12. X-ray detector 40
generates a signal representative of the detected radiation. In one
embodiment, one or more collimators (not shown) are positioned
between container 12 and X-ray detector 40 for facilitating
preventing or limiting scattered radiation energy from damaging
X-ray detector 40.
[0031] System 10 facilitates obtaining a large number of precise
X-ray views, which are then used to reconstruct a volumetric image
of container 12. The image is a mapping of the CT number for each
volume element regardless of the superposition of objects or
materials within container 12. In one embodiment, an imaging system
is coupled to X-ray detectors 40 to process the image data for
producing a two-dimensional or three-dimensional map of the
container and its contents. The reconstructed images are processed
to determine a CT number, density and/or atomic number of container
12 being scanned. Analysis of these images facilitates determining
the type of material contained within container 12, for
example.
[0032] In one embodiment, a data collection system 50 is
operatively coupled to and in signal communication with X-ray
detector 40. Data collection system 50 is configured to receive the
signals generated and transmitted by X-ray detector 40. A processor
60 is operatively coupled to data collection system 50. Processor
60 is configured to produce or generate an image of container 12
and its contents and process the produced image for facilitating
determining the material content of container 12. More
specifically, in one embodiment data collection system 50 and/or
processor 60 produces at least one attenuation map based upon the
signals received from X-ray detector 40. Utilizing the attenuation
map(s), at least one image of the contents is reconstructed and a
CT number, a density and/or an atomic number of the contents is
inferred from the reconstructed image(s). When data is collected
using a single energy mode, the CT image is analyzed. When data is
collected using a multiple energy mode, two or more CT images of
the cargo are produced. Based on these CT images, density and/or
atomic maps of the cargo can be produced. The CT images, the
density and/or atomic number images are analyzed to infer the
presence of contraband such as explosives, special nuclear and
shielding materials and/or to perform cargo manifest
verification.
[0033] In alternative embodiments, one processor 60 or more than
one processor 60 may be used to generate and/or process the
container image. In one embodiment, system 10 also includes a
display device 62, a memory device 64 and/or an input device 66
operatively coupled to data collection system 50 and/or processor
60.
[0034] As used herein, the term processor is not limited to only
integrated circuits referred to in the art as a processor, but
broadly refers to a computer, a microcontroller, a microcomputer, a
programmable logic controller, an application specific integrated
circuit and any other programmable circuit. The processor may also
include a storage device and/or an input device, such as a mouse
and/or a keyboard.
[0035] X-ray source 30 emits x-rays in an energy range, which is
dependent on a voltage applied by a power source to X-ray source
30. A primary beam 70 shown in FIG. 1, such as a fan beam or cone
beam, is generated. Primary beam 70 passes through container 12
positioned on platform 20 and X-ray detector 40, positioned on the
opposing side of platform 20, measures an intensity of primary beam
70. In one embodiment, X-ray detector 40 measures the x-rays in an
energy-sensitive manner by outputting a plurality of electrical
output signals dependent on a plurality of energies of x-ray quanta
detected from within primary beam 70.
[0036] In one embodiment, system 10 is configured to determine
and/or confirm a presence of fissile material and/or passively
detect the presence of radioactive materials in container 12. In
conventional scanning systems, container 12 is moved to a second
platform for conducting a fissile material and/or passive detection
scan of container 12, if desired. Unlike conventional scanning
systems, system 10 provides a reliable method for detecting and/or
confirming a presence of fissile material in container 12 without
rerouting or repositioning container 12. In a particular
embodiment, a subsystem performs an active interrogation of
container 12 with high energy X-rays, which induces fission in
fissile material potentially contained within container 12,
commonly referred to as photofission. Following photofission,
decaying products emit delayed gamma rays and/or delayed neutrons,
which provide a characteristics signature for a particular fissile
material. In an alternative embodiment, the system detects the
increased number of prompt neutrons to infer the presence of
fissile materials. System 10 is configured to analyze any
characteristics signature produced during the scanning process to
determine the presence of fissile material contained within
container 12. The system and/or subsystem as described herein may
be utilized in cooperation with any suitable CT scanning system for
detecting and/or confirming a presence of fissile material in an
object, such as a container.
[0037] At least one neutron detector 135 and at least one gamma-ray
detector 137 are positioned with respect to platform 20. In one
embodiment, neutron detector 135 and gamma-ray detector 137 are
configured to detect radiation resulting from fission of a fissile
material. The fission is induced by a beam with an energy
distribution produced by X-ray source 30. This energy distribution
may be the same or similar to the energy distribution utilized
during the CT scanning process. Alternatively, this energy
distribution may be different than the energy distribution utilized
during the CT scanning process. Further, the photofission process
may take place simultaneously with the CT scanning process or
separately. For example, a separate scan during the photofission
process may be performed if suspicious cargo or an area of concern
is detected, or a threat of fissile material within container 12 is
suspected.
[0038] During the photofission process, neutron detector 135 and
gamma-ray detector 137 generate at least one signal representative
of detected radiation resulting from the fission of the fissile
material. A data collection system and/or a processor, as described
below, are operatively coupled to neutron detector 135 and
gamma-ray detector 137 to receive the generated signal(s) and
detect and/or confirm a presence of fissile material.
[0039] In a further embodiment, neutron detector 135 and gamma-ray
detector 137 are utilized for detecting passively the presence of
radioactive materials. The passive detection can proceed while
container 12 rotates to minimize the time to obtain the required
statistical accuracy.
[0040] In one embodiment, X-ray source 30 includes a Bremstrahlung
source for generating radiation having a high energy distribution,
such as an energy distribution greater than about 1 MV. System 10
can be retrofitted with fissile material confirmation capability
based on differential die-away or detection of delayed radiation
induced by photofission. Further, the subsystem can be used to
perform passive inspection. In one embodiment, neutron detector 135
and gamma-ray detector 137 are configured to perform a passive scan
of container 12 to detect radioactive materials.
[0041] The above-described system and method facilitates inspecting
cargo containers efficiently and reliably. More specifically, the
system and method facilitate effectively inspecting cargo
containers using a Megavolt CT scanning system to automatically
detect contraband and to distinguish the atomic number of
materials.
[0042] Exemplary embodiments of a system and method for inspecting
cargo are described above in detail. The system and method are not
limited to the specific embodiments described herein, but rather,
components of the system and/or steps of the method may be utilized
independently and separately from other components and/or steps
described herein. Further, the described system components and/or
method steps can also be defined in, or used in combination with,
other systems and/or methods, and are not limited to practice with
only the system and method as described herein.
[0043] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
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